POS1184 A CASE OF DELAYED DIAGNOSIS OF MUCKLE WELLS SYNDROME- AN EXTREMELY RARE BUT IMPORTANT DIFFERENTIAL OF INFLAMMATORY ARTHRITIS IN A RHEUMATOLOGY CLINIC
Authors: A. Anjum, R. Davies, R. Asif
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Muckle wells syndrome (MWS) is one of the rare clinical phenotypes of Cyropyrin associated periodic syndromes (CAPS), driven by Interleukin-1 mediated systemic inflammation.<sup>[1]</sup> A typical presentation includes episodic fever, urticarial rash and arthralgia but can also result in episodic inflammatory arthritis and sensorineural hearing impairment. Secondary amyloidosis is the most feared complication especially in patients with untreated active disease.<sup>[2]</sup> <h3>Objectives</h3> We present a case of a 32 years old male, with history of episodic pain and swelling of the right knee for 2 years before presentation to rheumatology clinic. <h3>Methods</h3> Over the years, prior to rheumatology review he was seen by multiple specialties for varied unexplained symptoms including ENT for progressive sensorineural hearing impairment, dermatology for intermittent childhood onset eczematous rash and by ophthalmology for episodic idiopathic iritis and uveitis. He was also seen by haematology for an episode of cervical lymphadenopathy with no definite cause identified. There was no history of inflammatory back pain, psoriasis or Inflammatory bowel disease. Of note, his father had severe sensorineural hearing loss and his brother had a diagnosis of undifferentiated inflammatory arthritis at a young age. On initial rheumatology assessment he had a moderate knee right knee effusion and an erythematous non-specific rash over his upper back. A review of previous investigations showed raised inflammatory markers (CRP 93). A prior MRI right knee showed areas of synovial hypertrophy with a moderate knee effusion. <h3>Results</h3> Subsequent investigations were negative for Rheumatoid factor, Anti-CCP Ab, ANA, ENA, ANCA, HLA B27 and HLA B-51. The initial rheumatology impression was of an isolated seronegative inflammatory arthritis of the right knee but given other unexplained symptoms and family history we investigated for autoinflammatory disorders. Subsequent genetic screen was positive for NLRP3 gene confirming Muckle Wells syndrome as the unifying diagnosis. This case was also discussed with the National Autoinflammatory Disease Centre, UCL London and he has recently been commenced on Anakinra. <h3>Conclusion</h3> Targeted IL-1 inhibitors can prevent secondary amyloidosis. Effect on hearing impairment is uncertain but can be reversed in some cases. The heterogeneity of presentation poses a significant diagnostic challenge, however given the clear efficacy of available treatment options, an early diagnosis is extremely important to improve symptoms and prevent serious organ damage from secondary amyloid. <b>2</b>) Although episodic pyrexia is considered a hallmark of autoinflammatory disorders, its absence does not exclude CAPS, as was the case in our patient. <b>3</b>) We recommend considering this diagnosis as a differential of seronegative inflammatory arthritis, especially in younger patients with unexplained multi systemic involvement and suspicious family history. <h3>References</h3> [1]Masters SL, Simon A, Aksentijevich I, <i>et al</i>. Horror autoinflammaticus: the molecular pathophysiology of autoinflammatory disease (*). <i>Annu Rev Immunol</i> 2009;27:621–68. [2]Scarpioni R, Ricardi M, Albertazzi V. Secondary amyloidosis in autoinflammatory diseases and the role of inflammation in renal damage. <i>World J Nephrol</i> 2016; 5(1): 6675 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.